How can a basketball player reliably land his free throw in the basket, and yet still miss occasionally under nominally identical circumstances? While such skills are a paragon of motor expertise, even seemingly mundane actions also require surprising dexterity. When carrying a full cup of coffee, we exhibit motor skill that is far beyond what is typically studied in the laboratory. Specifically, when interacting with objects - the essence of any tool use -, successful actions require fine-grained control of interaction forces that have been beyond the purview of neuroscience to date. The proposed research examines the neural basis of motor expertise by bringing rich interactive tasks into the laboratory. The two PIs combine their long-standing experience in computational motor control and neurophysiology to study novel behavioral paradigms both in humans and non-human primates. Building on conceptual and computational overlap in their respective research, where skill is associated with low-dimensional structure in high-dimensional neural and behavioral redundant spaces, they will test the overall hypothesis that patterns of neural activity exhibit many of the characteristics of the behavior. Two aims will study two examples of motor skill: throwing an object and transporting an object with internal dynamics, both rendered in virtual environments. Parallel experiments in humans and primates will generate rich behavioral data that will be matched with intracortical recordings in the cerebral cortex of non-human primates. To date, non-human primate studies have necessitated that animals perform near-identical repetitions of simple behaviors to facilitate the analysis of neural activity. Now, modern multi-neuronal recording techniques make it possible to embrace more sophisticated real-world behaviors and address core principles of movement discovered in human motor control: high dimensionality, redundancy, and the ever-present variability. This research will develop a suite of computational tools that afford the analysis of behavioral and neural data with commensurate techniques and sophistication. This research will be transformative as it advances the motor challenges examined and brings insights from intracortical neurophysiology closer to understanding of human motor expertise. These scientific insights will channel into a large range of outreach activities to achieve broader impacts for the general public. RELEVANCE (See instructions): Patients with neurological disorders such as stroke face challenges in their daily activities, grasping a cup to bring to their mouths to drink; these actions are essentially interactive tool use. This research seeks insights into neural activation during such skilled actions and interactions to get closer to understand neural activity in tasks relevant in real life. Extending from PI Batista?s experience, neuroprosthetics and brain-machine interfaces are direct clinical application that may benefit from our findings and recovery